This invention relates to an image forming apparatus, more specifically, the invention relates to an apparatus for reproducing a copy image according to either a positive original image or a negative original image.
As an example of such an apparatus, there is known a microfilm reader printer which may project a reduced image recorded on a microfilm onto a screen and also reproduce copies of the microfilm image if desired. Microfilms have been extensively used for storing and retrieving image information. Generally, the images recorded on microfilms are roughly classified into two categories, i.e., positive images and negative images which are selected according to a type of an original image. Therefore, two types of developing devices are necessary in order to reproduce a copy image from these two different kinds of microfilm images in conformity with the condition of the recorded image. To meet this requirement, a developing device for reproducing a positive copy image from a positive microfilm image and another developing device for reproducing a positive copy image from a negative microfilm image are prepared and only one of these developing devices is mounted on the microfilm reader printer according to the kind of microfilm images. It is, however, necessary to replace the developing device each time the kind of image to be developed is changed. The operation of replacing the developing device takes some time and requires a great deal of effort. This system, therefore, is inferior in view of its cumbersome operability.